The demand for electricity can be met in two different ways. The main method is to build large centralized projects to generate and transmit the electricity required. Many of these projects have caused unpleasant environmental effects such as air or radiationpollution and the flooding of large areas of land.

Distributed generation creates power on a smaller scale at locations on the electricity network. These sites often generate electricity as a byproduct of other industry such as using gas from landfills to power turbines.

Rotating turbines attached to electrical generators produce most commercially available electricity. Turbines are driven by a fluid which acts as an intermediate energy carrier. The fluids typically used are:

wind - Most wind turbines generate electricity from naturally occurring wind. Solar updraft towers use wind that is artificially produced inside the chimney by heating it with sunlight.

hot gases - Turbines are driven directly by gases produced by the combustion of natural gas or oil.

Combined cycle gas turbine plants are driven by both steam and gas. They generate power by burning natural gas in a gas turbine and use residual heat to generate additional electricity from steam. These plants offer efficiencies of up to 60%.

Small electricity generators are often powered by reciprocating engines burning diesel fuel, biogas or natural gas. Diesel engines are often used for back up generation, usually at low voltages. Biogas is often combusted where it is produced, such as a landfill or wastewater treatment plant, with a reciprocating engine or a microturbine, which is a small gas turbine.

Unlike the solar heat concentrators, photovoltaic panels convert sunlight directly to electricity. Although sunlight is free, solar panels cost a lot of money to make and have only a 10-20% conversion efficiency. Until recently, photovoltaics were most commonly used in remote sites where there is no access to a commercial power grid, or as an extra electricity source for individual homes and businesses. Recent advances in manufacturing efficiency and photovoltaic technology, combined with subsidies driven by environmental concerns, have dramatically accelerated the deployment of solar panels. Installed solar capacity is growing by 30% per year in several regions including Germany, Japan, California and New Jersey.